1. Field of the Invention
The invention relates to the field of earth boring tools and in particular to apparatus to measure the flow of hydraulic fluid or drilling mud through a drill string.
2. Description of the Prior Art
Control of the petroleum oil well is largely accomplished through the control of mud or hydraulic fluid pumped into the drill string. A result, the drill operators have developed the ability and the means for controlling the flow rate hydraulic mud within the drill string to a degree of reasonable accuracy and control.
On the other hand, the communication with downhole equipment while drilling has been very difficult to achieve with any degree of practical acceptability. Attempts to communicate with downhole equipment from the well surface through electrical means or through mud pulsation techniques have been possible, but often suffer from unreliability under field conditions. Generally, it is very difficult to achieve the signal resolution necessary to unambiguously transmit distinct commands downhole.
Therefore, what is needed is a method and apparatus whereby communication of information downhole can be reliably and unambiguously transmitted under all field conditions.